In a person authentication, a risk of plagiarism is relatively high with use of a password authentication, an ID card authentication or the like that are widely used conventionally. And so, a biometric authentication such as a fingerprint authentication attracts attention as a person authentication having higher reliability and is being used in many situations.
It is a problem of the biometric authentication that an authentication is difficult. In order to solve the problem, a method in which biometric authentication and an alternate authentication (for example a password authentication) are combined is disclosed (see Patent Documents 1 to 3). In the methods, the password authentication is performed when the biometric authentication is difficult.    Patent Document 1: Japanese Laid-Open Patent Publication No. 9-297844    Patent Document 2: Japanese Laid-Open Patent Publication No. 2006-107340    Patent Document 3: Japanese Laid-Open Patent Publication No. 2001-307102